Method of making pavement.



UNITED STATES PATENT OFFICE. WALTER E. HASSAM, F WORCESTER, AND HAROLD PARKER, OF LAIQTCASTER, MASSA- CHUSETTS, ASSIGNORS TO HASSAM PAVING COMPANY, A CORPORATION OF -NEASSA- CHUSETTS. r

METHOD OF MAKING PAVEMENT.

j ,191 3()3 Specification of Letters Patent.

No Drawing.

cester and State of Massachusetts, have invented a new and useful Method of Making Pavement, of which the following is a specification.

This invention relates to an improved method of making the pavement shown, de-

scribed and claimed in the application for p patent filed on even date herewith, by the said Walter E. Hassam Serial No. 712672.

Said. application for patent relates to animprovement on Letters-Patent granted to him May 1, 1906, No. 819,652 ona Pavement and process of laying the same. By said patent he provides a pavement, by laying on the level road bed a layer or stratum of naked" or uncoated stone; by rolling the stone in its uncoated or clean condition; by applying a grout to fill" the voids therein; and by placing a .suitable wearing surface thereon. The improvement contained in said application for patent consists in substance in providing a cone ete foundation or pavement of the charac er shown, described and claimed in said-patent, with a smooth or top surface, and in applying a thin layer of-hot bitumen thereto, which bituminous layer is drifted and rolled with screened pea stone or suitable sand or gravel. In experimenting with the improvement of said application, we have discovered that the-bituminous layer can be caused to adhere much closer to the concrete foundation if the same is applied thereto under pressure. This we attribute to the fact that by applying the hot bitumen to the concrete foundation in small jets under heavy pressure, all dust or loose particles are swept aside, air bubbles prevented, and if the concrete foundation is left' or made slightly moist, when the hot bitumen is applie under pressure, an action takes place which causes a very firm adherence.

The improved method is practised as follows :The road which is to receive the pavement is first leveled off" or prepared and brought to a solid sub-grade of exact crosssection by rolling or tamping, as may be necessary. Then on this road a layer or Application filed August 1, 1912. Serial No. 712,803.

stratum of uncoated broken stone of about from one and one-half inches to two and one-halfinc hes in diameter is laid so that it will have a uniform thickness. This layer of uncoated stone is then rolled with a heavy roller, or otherwise compressed in its naked or uncoated condition to reduce-the voids therein to a minimum, to get the stones into as intimate contact with each other as possible, and to get as much stone into a given thickness as possible. This rolling and comacting is carried on until a stone layer. of suitable thickness is provided. A thin grout consisting of Portland cement, one part;

sand, two or more parts; and enough water to form a creamy consistency is then poured upon the stone layer until all the voids therein are filled and until the. grout flushes to the surface. During this step, or immediately thereafter, the stone layer is lightly rolled or compressed to obtain as smooth and even top surface as is possible (and to' force the grout into every portion of the mass). The foundation or concrete thus formed is allowed to set until it becomes hard (and thoroughly set) with a very smooth even top surface. This top surface is then slightly moistened with Water. Then the smooth moistened top surface of the concrete is covered with a very thin layer of bitumen or bituminous compound heated to a temperature'of between 200 and 300 degrees F., and applied in fine jets under pressure. This application can be made by any suitable spraying and pressure machine and is preferably carried on by a pumping spraying machine having nozzles arranged five to, ten inches above the ground and having a pump or other means of applying pressure which will force the hot bitumen out through the nozzles in jet form at about 80 pounds pressure. This application of hot bitumen under pressure to the concrete foundation, will cause a very firm adherence of the bitumen to the concrete. Immediately after this thin bituminous coat is applied, the same is drifted with screened pea stone or suitable sand or gravel and rolled with a'.

light roller, sufficient stone, sand or gravel being applied to absorb anysurplus bitumen.

A plurality of layers of bitumen and sand, stone or gravel preferably are applied in this manner so as to make up a mat or wearing herence between the bituminous surface and the concrete.

By this method of construction, a superior Wearing surface can be produced because the hot bitumen can be very quickly applied, as only avery thin (and uniform) layer is required; and the method is very economical, because only a relatively small amount of bitumen is needed, even if a plurality of layers are applied. The pavement thus con structed has the great rigidity and strength of concrete, and has additionally, an ineX- pensive resilient wearing surface which is practically du'stless, which gives the proper grip for wheels and horses, and which can be very readily repaired.

The proportions herein specified may be varied by a skilled engineer without departing from the scope of our invention as expressed in the claims.

Having thus fully described our invention, What We claim and desire to secure by Letters-Patent is 1. The method of making a pavement, which consists in laying a concrete foundation, moistening the same, and applying one or more thin layers of hot bitumen to the foundation under pressure.

2. The method of making a pavement, which consists in laying a concrete foundation, moistening the same, applying one or more thin layers of hot bitumen to the same under pressure, and rolling sand. pea stone or gravel into the bituminous layer.

In testimony whereof We have hereunto set our hands, in the presence of two subscribing itnesses.

WALTER E. HASSAM. HAROLD PARKER.

Witnesses:

CHAS. D. LIvERMoRE, Gnoncn MAGUIRE. 

